The present invention relates to a power-supply unit for automobiles, and more particular, to a power-supply unit for automobiles, in which electric power is supplied to an on-board electrically-driven brake device for generating braking forces with the use of electric power supplied from an electric power supply source.
Conventionally, an electrically-driven brake device for actuating electric motors with electric power and electric signals to generate braking forces has been known, which comprises two independent electric power sources E1, E2 and in which four wheel units are divided diagonally into two systems, the electric source E1 supplies energy to two wheel units for a left front wheel and a right rear wheel, and the electric source E2 supplies energy to two wheel units for a right front wheel and a left rear wheel (for example, see JP-A-2000-16262, page 3 & FIG. 1).
With the above device, a power-supply unit of the electrically-driven brake device comprises two electric power supply sources, and the two electric power supply sources independently supply electric power to the two divided systems of the device. Therefore, even when failure occurs in one of the electric power supply sources and so one system of the electrically-driven brake device does not operate normally, the other system of the electrically-driven brake device operates normally, so that it is possible to realize an electrically-driven brake device of high reliability.
In the above-described conventional electrically-driven brake device, reliability is heightened by the two electric power supply sources and the divided two systems, so that the electrically-driven brake device and the power-supply unit are in some cases made complex in constitution. In order to supply an electrically-driven brake device of high reliability while holding down an increase in cost, the electrically-driven brake device and the power-supply unit are desirably able to ensure sufficient braking forces at all times without complexity in constitution.